The behavior of dielectric and microwave properties against sintering temperature has been carried out on CaO–SiO 2 –B 2 O 3 ceramic matrix composites with ZrO 2 addition. The results indicated that ZrO 2 addition was advantageous to improve the dielectric and microwave properties. X-ray diffraction (XRD) patterns show that the major crystalline β-CaSiO 3 and a little SiO 2 phase existed at the temperature ranging from 950°C to 1050°C. At 0.5wt% ZrO 2 , CaO–SiO 2 –B 2 O 3 ceramic matrix composites sintered at 1000°C possess good dielectric properties: ɛ r =5.85, tanδ=1.59×10 −4 (1MHz) and excellent microwave properties: ɛ r =5.52, Q·f=28,487GHz (11.11GHz). The permittivity of Zr-doped CaO–SiO 2 –B 2 O 3 ceramic matrix composites exhibited very little temperature dependence, which was less than ±2% over the temperature range of −50 to 150°C. Moreover, the ZrO 2 -doped CaO–SiO 2 –B 2 O 3 ceramic matrix composites have low permittivity below 5.5 over a wide frequency range from 20Hz to 1MHz.